A cross that reads Not Forgotten lies next to an unmarked grave at the Terrace Park cemetery just outside Holtville, California. Behind a row of hedges at the otherwise normal and nondescript cemetery lies a dirt field with hundreds of other such graves, reportedly containing immigrants who died crossing the border whose remains were never identified

A worker labours at a romaine lettuce farm outside San Luis, Arizona. The workers, most of whom live in Mexico, cross the border each day by bus to various farms around San Luis. During their eight-hour shift, they break twice for 15 minutes, said the workers

A US Border Patrol guard checks under the bridge crossing at El Paso, Texas, which lies just across the border from Ciudad Juarez, a frontline in Mexico's increasingly violent and bloody war against drug cartels

People await relatives at the border in Nogales, Arizona. A town of about 20,000 people, it lies just north of the city of Nogales, Mexico, which has a population estimated at nearly 10 times its northern neighbour. Nogales, Mexico has been affected by drug violence, mostly in the area south of the city, and remains a popular point for drug smugglers and those trying to cross illegally

A man in need of medical assistance sits in pain at an aid centre in Nogales, Mexico. The centre serves people who have been recently deported to Mexico, either for trying to cross illegally or already residing illegally in the US

Betcy and Marco Cruz talk to relatives through the fence at Calexico, California. The thriving border town of 39,000 sits just north of Mexicali, Mexico, a city of nearly one million. The city is seen as prime crossing point for goods

Houses on the other side of the border between the US and Mexico from Nogales, Arizona. A town of about 20,000 people, it lies just north of the city of Nogales, Mexico, which has a population estimated at nearly ten times that number. Nogales, Mexico has been affected by drug violence, mostly in the area south of the city, and remains a popular point for drug smugglers and those trying to cross illegally